On Thu, Aug 03, 2023 at 04:32:07PM +0200, David Hildenbrand wrote:
> Let's extend mmap_and_merge_range() to test if anything in the current
> process was merged. range_maps_duplicates() is too unreliable for that
> use case, so instead look at KSM stats.
>
> Trigger a complete unmerge first, to cleanup the stable tree and
> stabilize accounting of merged pages.
>
> Note that we're using /proc/self/ksm_merging_pages instead of
> /proc/self/ksm_stat, because that one is available in more existing
> kernels.
>
> If /proc/self/ksm_merging_pages can't be opened, we can't perform any
> checks and simply skip them.
>
> We have to special-case the shared zeropage for now. But the only user
> -- test_unmerge_zero_pages() -- performs its own merge checks.
>
> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Acked-by: Peter Xu <peterx@xxxxxxxxxx>
One nitpick:
> ---
> .../selftests/mm/ksm_functional_tests.c | 47 +++++++++++++++++++
> 1 file changed, 47 insertions(+)
>
> diff --git a/tools/testing/selftests/mm/ksm_functional_tests.c b/tools/testing/selftests/mm/ksm_functional_tests.c
> index 0de9d33cd565..cb63b600cb4f 100644
> --- a/tools/testing/selftests/mm/ksm_functional_tests.c
> +++ b/tools/testing/selftests/mm/ksm_functional_tests.c
> @@ -30,6 +30,7 @@
> static int ksm_fd;
> static int ksm_full_scans_fd;
> static int proc_self_ksm_stat_fd;
> +static int proc_self_ksm_merging_pages_fd;
> static int ksm_use_zero_pages_fd;
> static int pagemap_fd;
> static size_t pagesize;
> @@ -88,6 +89,22 @@ static long get_my_ksm_zero_pages(void)
> return my_ksm_zero_pages;
> }
>
> +static long get_my_merging_pages(void)
> +{
> + char buf[10];
> + ssize_t ret;
> +
> + if (proc_self_ksm_merging_pages_fd < 0)
> + return proc_self_ksm_merging_pages_fd;
Better do the fds check all in main(), e.g. not all callers below considers
negative values, so -1 can pass "if (get_my_merging_pages())" etc.
> +
> + ret = pread(proc_self_ksm_merging_pages_fd, buf, sizeof(buf) - 1, 0);
> + if (ret <= 0)
> + return -errno;
> + buf[ret] = 0;
> +
> + return strtol(buf, NULL, 10);
> +}
--
Peter Xu
